Acquired angioedema in juvenile systemic lupus erythematosus: case-based review

An acquired form of angioedema that is clinically similar but scarcer than the hereditary form may be caused, even more rarely, by the presence of an underlying autoimmune disease. We report a previously healthy 16-year-old girl with an acquired angioedema as a rare and initial presentation of systemic lupus erythematosus. The patient had no previous angioedema attack and no family history. She did not have any chronic diseases and did not use any medicine regularly. The patient was diagnosed with systemic lupus erythematosus with the presence of polyarthralgia, angioedema, leucopenia, and positivity of immunologic criteria. Her edema resolved with high-dose methylprednisolone and hydroxychloroquine slowly. In conclusion, new-onset angioedema in adolescent girls should be investigated to evaluate autoimmunity and the possibility of systemic lupus erythematosus. The related literature on acquired angioedema associated with systemic lupus erythematosus is also reviewed.

Hypercomplementemia in adult patients with IgA nephropathy

IgA nephropathy (IgAN) is the most common form of chronic glomerulonephritis. Although glomerular deposition of complement components is well known, the evidence of serological complement activation in IgAN is inconclusive. We hypothesized that serum levels of complement components and regulatory proteins in patients with IgAN are correlated with its pathogenesis. In the present study we measured complement components in 50 patients with IgAN and 50 healthy volunteers. C5, C1 inhibitor, factor B, C4 binding protein, factor H, and factor I were measured with the use of single radial immunodiffusion. Mannose-binding lectin (MBL) and properdin (P) were measured by enzyme-linked immunosorbent assay (ELISA). The correlations among complements in the sera of patients with clinical gradings for IgAN (i.e., the good prognosis group, relatively good prognosis group, relatively poor prognosis group, and poor prognosis group) were evaluated. CH50, C4, factor B, P, factor I, and factor H were significantly higher in IgAN patients than in healthy controls. There were significant correlations between C5 and C4 binding protein, between C3 and C5, or between C4 and factor B in patients with IgAN. In the poor prognosis group, C4 binding protein was significantly higher than in the other groups of IgAN patients. hypercomplementemia occurs in IgAN and is associated with an increase in complement regulatory protein (CRP). C4 binding protein analyses can be used to predict disease prognosis.

C1 inhibitor, C3 activator, IgG, IgA, and IgM titers in Nigerian sickle cell disease patients with plasmodium falciparum

BACKGROUND

Sickle cell disease (HbSS) is a major health problem in Nigeria and malaria has been implicated as a leading cause of morbidity/mortality in sickle cell disease patients. Few reasons were put forward to explain the observed morbidity/mortality of HbSS subjects due to Plasmodium falciparum (P. falciparum) malaria.

OBJECTIVES

To determine the level of immunoglobulin classes (IgM, IgA, and IgG) and regulators of complement system (C1 inhibitor and C3 activator) in Nigerian HbSS patients with and without P. falciparum parasitemia.

METHODS

A total of 64 subjects were considered, including 10 HbSS genotypic subjects with P. falciparum parasitemia (HbSS+PfM), 18 HbAA genotypic subjects with P. falciparum parasitemia (HbAA+PfM), 20 HbSS without P. falciparum parasitemia (HbSS-PfM), and 16 HbAA genotypic subjects without P. falciparum parasitemia (HbAA-PfM). IgM, IgA, IgG, C1 inhibitor, and C3 activator titers were quantified by single radial immunodiffusion method.

RESULTS

The mean levels of IgG in HbSS+PfM (2373.90+/-1772.81mg/dl) and HbAA+PfM (1868.80+/-0.00mg/dl) were significantly higher compared with HbSS-PfM (644.55+/-171.15mg/dl) or HbAA-PfM (659.75+/-158.01mg/dl) patients. HbAA-PfM subjects had the lowest level of IgM (67.27+/-63.7mg/dl), though no significant difference was observed comparing mean levels of IgM between the four groups. IgA titer was significantly higher in HbSS-PfM patients (249.00+/-94.8mg/dl) compared with HbAA-PfM (p<0.05), HbAA+PfM (p<0.05), or HbSS+PfM (p<0.05). The mean values of C1 inhibitor were lower in HbSS+PfM and HbAA+PfM compared with HbSS-PfM or HbAA-PfM. However, HbAA+PfM had a significantly lower value of C1 inhibitor compared with HbAA-PfM (p<0.01). C3 activator was highest in HbSS-PfM (17.10+/-7.35mg/dl) and was significantly higher compared with HbSS+PfM (p<0.05).

CONCLUSION

Increased C1 inhibitor and decreased C3 activator in HbSS+PfM compared with HbAA+PfM shows that deranged regulation of complement factors may be responsible for increased susceptibility of HbSS to P. falciparum malaria.

N-linked glycosylation at Asn3 and the positively charged residues within the amino-terminal domain of the c1 inhibitor are required for interaction of the C1 Inhibitor with Salmonella enterica serovar typhimurium lipopolysaccharide and lipid A

The C1 inhibitor (C1INH), a plasma complement regulatory protein, prevents endotoxin shock, at least partially via the direct interaction of its amino-terminal heavily glycosylated nonserpin region with gram-negative bacterial lipopolysaccharide (LPS). To further characterize the potential LPS-binding site(s) within the amino-terminal domain, mutations were introduced into C1INH at the three N-linked glycosylation sites and at the four positively charged amino acid residues. A mutant in which Asn(3) was replaced with Ala was markedly less effective in its binding to LPS, while substitution of Asn(47) or Asn(59) had little effect on binding. The mutation of C1INH at all four positively charged amino acid residues (Arg(18), Lys(22), Lys(30), and Lys(55)) resulted in near-complete failure to interact with LPS. The C1INH mutants that did not bind to LPS also did not suppress LPS binding or LPS-induced up-regulation of tumor necrosis factor alpha mRNA expression in RAW 264.7 macrophages. In addition, the binding of C1INH mutants to diphosphoryl lipid A was decreased in comparison with that of recombinant wild-type C1INH. Therefore, the interaction of C1INH with gram-negative bacterial LPS is dependent both on the N-linked carbohydrate at Asn(3) and on the positively charged residues within the amino-terminal domain.

Deficiencies of C1 inhibitor

Hereditary and acquired deficiencies of the C1 inhibitor result in a single prominent symptom, namely angioedema. Angioedema may involve the skin, the gastrointestinal tract or the upper airway. Genetically determined defects in C1INH cause hereditary angioedema. The defect may be acquired as the result of an auto-antibody to C1INH or be due to the generation of anti-idiotypic antibody to monoclonal immunoglobulins as occurs in various B cell lymphoproliferative diseases. Androgens provide prophylaxis against attacks of angioedema. There is no widely approved treatment for acute attacks of angioedema although several promising drugs are now in the final stages of clinical trials.

The pathophysiology of hereditary angioedema

Hereditary angioedema (HAE), characterized by recurrent episodes of angioedema involving the skin, or the mucosa of the upper respiratory or the gastrointestinal tracts, results from heterozygosity for deficiency of the serine proteinase inhibitor (serpin), C1 inhibitor (C1INH). The primary biological role of C1INH is to regulate activation of the complement system, the contact system, and the intrinsic coagulation system. During attacks of angioedema, together with decreasing levels of C1INH, the complement and contact systems are activated: C2 and C4 levels fall and high molecular weight kininogen is cleaved. Although previous data suggested that symptoms in HAE might be mediated via complement system activation, a combination of recent clinical data, in vitro studies, and analysis of C1INH-deficient mice all indicate that the major mediator of angioedema is bradykinin: (1) a vascular permeability enhancing factor can be generated in vitro in C1INH-depleted, C2-deficient plasma, but not from C1INH-depleted, contact system-deficient plasma; this factor was identified by sequence analysis as bradykinin; (2) bradykinin can be detected in the plasma of HAE patients during attacks of angioedema; (3) in several members of one family, expression of a C1INH variant that inhibits contact system proteases but has defective inhibition of C1r and C1s does not result in HAE; (4) C1INH-deficient (C1INH-/-) mice have a defect in vascular permeability that is suppressed by treatment with specific plasma kallikrein inhibitors and by bradykinin type 2 receptor (Bk2R) antagonists, and is eliminated in C1INH-/-, Bk2R-/- double-deficient mice.

Metabolic alteration of the N-glycan structure of a protein from patients with a heterozygous protein deficiency

Glycosylation, an important post-translation modification, could alter biological activity or influence the clearance rates of glycoproteins. We report here the first example of a heterozygous protein deficiency leading to metabolic alteration of N-glycan structures in residual secreted protein. Analysis of C1 esterase inhibitor (C1INH) glycans from normal individuals and patients with hereditary deficiency of C1INH demonstrated identical O-glycan structures but the N-glycans of patients with a heterozygous genetic deficiency were small, highly charged and lacked sialidase releasable N-acetylneuraminic acid. Structural studies indicate that the charge character of these aberrant N-glycan structures may result from the presence of mannose-6-phosphate residues. These residues might facilitate secretion of C1INH through an alternate lysosomal pathway, possibly serving as a compensatory mechanism to enhance plasma levels of C1INH in these deficient patients.

Current and future therapy for hereditary angioedema

Hereditary angioedema (HAE) is an autosomal dominant disease characterized by recurrent episodes of potentially life-threatening angioedema. Attacks of angioedema in HAE patients typically last 3 or more days, begin during childhood, and continue to occur throughout life. Tragically, patients with HAE continue to die as a direct consequence of the disease. Minimizing the morbidity and mortality associated with HAE requires both effective treatment of acute attacks as well as strategies to prevent HAE attacks. While there is currently no effective therapy available in the United States for the treatment of acute attacks of HAE, several molecules have demonstrated impressive efficacy in this setting, and it is likely that one or more of these new drugs will become available in the United States soon. This article will review both the current and the future therapeutic options for the treatment of HAE.

Identification of HIV-1 protease cleavage site in human C1-inhibitor

We have investigated the ability of HIV-1 protease to cleave human complement proteins of the classical complement pathway: C1q, C2 and C4 as well as the regulatory protein, C1-inhibitor. Purified complement proteins were incubated with recombinant HIV-1 protease in vitro and analyzed by SDS-PAGE and immunoblotting assay. The only cleavage site was found in N-terminal region of C1-inhibitor, and it was located between residues Leu-32 and Phe-33 as determined by amino acid sequence analysis of the 85 kDa proteolytic fragment after 12 Edman degradation cycles. The HIV-1 protease cleavage sites were not found in C1q, C2 and C4 protein. HIV-1 protease-susceptible site in N-terminal region of C1-inhibitor is very close to the cleavage sites of some other proteases that are able to induce N-terminal proteolysis of the protein.

Worsening fluid retention in a patient with hereditary angioedema and end-stage renal disease

A 60-year-old woman who was diagnosed with hereditary angioedema (HAE) developed nephrotic syndrome, with end-stage renal disease (ESRD) occurring about 2.5 years later. During her slide toward ESRD, she experienced three severe episodes of angioedema that each resulted in significant fluid retention. Though the therapeutic administration of C1-inhibitor concentrate was effective in controlling her angioedema, seemed ineffective in preventing her from developing ESRD requiring hemodialysis treatment. We theorized that the patient's low colloid osmolality and glomerular perfusion were important facilitators of her attacks of angioedema.

Influence of lactation parameters on the N-glycosylation of recombinant human C1 inhibitor isolated from the milk of transgenic rabbits

The large-scale production of recombinant biopharmaceutical glycoproteins in the milk of transgenic animals is becoming more widespread. However, in comparison with bacterial, plant cell, or cell culture production systems, little is known about the glycosylation machinery of the mammary gland, and hence on the glycosylation of recombinant glycoproteins produced in transgenic animals. Here the influence is presented of several lactation parameters on the N-glycosylation of recombinant C1 inhibitor (rhC1INH), a human serum glycoprotein, expressed in the milk of transgenic rabbits. Enzymatically released N-glycans of series of rhC1INH samples were fluorescently labeled and fractionated by HPLC. The major N-glycan structures on rhC1INH of pooled rabbit milk were similar to those on native human C1 inhibitor and recombinant human C1 inhibitor produced in transgenic mouse milk, with only the degree of sialylation and core fucosylation being lower. Analyses of individual animals furthermore showed slight interindividual differences; a decrease in the extent of sialylation, core fucosylation, and oligomannose-type glycosylation with the progress of lactation; and a positive correlation between expression level and oligomannose-type N-glycan content. However, when large quantities of rhC1INH were isolated for preclinical and clinical studies, highly consistent N-linked glycan profiles and monosaccharide compositions were found.

Approaches toward reversal of increased vascular permeability in C1 inhibitor deficient mice

C1 inhibitor (C1INH) deficient mice have increased vascular permeability that can be demonstrated by the extravasation of Evans Blue dye. This vascular leak is reversed with protease inhibitors, such as C1INH itself, DX88 (a recombinant variant Kunitz domain plasma kallikrein inhibitor), and the bradykinin receptor type 2 antagonist, Hoe140. The studies described here were undertaken for the following reasons: (1) To provide a more quantitative analysis of the effects of these interventions; (2) to provide data to further test the hypothesis that increased vascular permeability results from contact system activation with kallikrein-mediated release of bradykinin; (3) to test the hypothesis that the amino terminal non-serpin domain of C1INH modulates access to complex proteases, such as kallikrein complexed with high molecular weight kininogen (HK); and (4) to determine whether attenuated androgens or estrogens exert a direct effect on C1INH synthesis. To characterize the differences in these reagents, the dose-response and the rate of reappearance of increased vascular permeability in C1INH(-/-) mice were determined for the following agents: human plasma-derived C1INH, a recombinant Kunitz domain plasma kallikrein inhibitor (DX88), a bradykinin receptor antagonist (Hoe140), and a recombinant C1INH with an amino terminal truncation at amino acid 98 and substitution of the P2 Ala with a Val (Cserp98,A443V). C1INH and Cserp98,A443V were equivalent in activity, which provides further support for the hypothesis that the vascular leak is mediated by bradykinin and suggests that the amino terminal domain neither enhances nor interferes with access to kallikrein within the kallikrein-HK complex. DX88 was effective at very low doses, as was Hoe140. The duration of action of Hoe140 was quite prolonged. The data indicate that, in the mouse, neither danazol nor estrogens have a significant effect on C1INH synthesis.

Characterization of recombinant mannan-binding lectin-associated serine protease (MASP)-3 suggests an activation mechanism different from that of MASP-1 and MASP-2

Mannan-binding lectin (MBL)-associated serine proteases (MASP-1, -2, and -3) are homologous modular proteases that each associate with MBL and L- and H-ficolins, which are oligomeric serum lectins involved in innate immunity. To investigate its physicochemical, interaction, and enzymatic properties, human MASP-3 was expressed in insect cells. Ultracentrifugation analysis indicated that rMASP-3 sedimented as a homodimer (s(20,w) = 6.2 +/- 0.1 S) in the presence of Ca(2+), and as a monomer (s(20,w) = 4.6 +/- 0.1 S) in EDTA. As shown by surface plasmon resonance spectroscopy, it associated with both MBL (K(D) = 2.6 nM) and L-ficolin (K(D) = 7.2 nM). The protease was produced in a single-chain, proenzyme form, but underwent slow activation upon prolonged storage at 4 degrees C, resulting from cleavage at the Arg(430)-Ile(431) activation site. Activation was prevented in the presence of protease inhibitors iodoacetamide and 1,10-phenanthroline but was not abolished upon substitution of Ala for the active site Ser(645) of MASP-3, indicating extrinsic proteolysis. In contrast, the corresponding mutations Ser(627)-->Ala in MASP-1 and Ser(618)-->Ala in MASP-2 stabilized the latter in their proenzyme form. Likewise, the MASP-1 and MASP-2 mutants were each activated by their active counterparts, but MASP-3 S645A was not. Activated MASP-3 did not react with C1 inhibitor; had no activity on complement proteins C2, C4, and C3; and only cleaved the N-carboxybenzyloxyglycine-L-arginine thiobenzyl ester substrate to a significant extent. Based on these observations, it is postulated that MASP-3 activation and control involve mechanisms that are different from those of MASP-1 and -2.

Normal complement C4 values do not exclude hereditary angioedema

This report describes a patient with hereditary angioedema (HAE) in whom complement C4 values were consistently normal. There was a family history of HAE, for which the patient had previously been screened, but in view of her normal C4 values she was deemed unaffected. However, at 10 years of age she presented with an eight month history of episodes of swelling affecting her hands and recurrent episodes of abdominal pain over the previous few months. In view of the recent clinical history of swellings and the family history of HAE, C4 and C1 inhibitor (C1inh) were measured. The C4 concentration was found to be within the normal range but the C1inh value was low (0.07 g/litre; normal range, 0.18-0.37). The patient was started on tranexamic acid and at an outpatient review three months later her episodes of swelling were occurring less often and were less severe. Although recent papers have suggested that the diagnosis of HAE can be excluded if complement C4 concentrations are normal, this case highlights the fact that C4 concentrations can be normal in this condition, and it is recommended that both C4 and C1inh concentrations should be measured to exclude HAE.

[Determination of the functional activity, amount of C1 inhibitor, and autoantibodies as a tool for differential diagnosis of angioedema]

Aetiology of angioedema (and therefore the scheme of its treatment) can be different. Angioedema may be subdivided into four categories: hereditary and acquired angioedemas, allergies and vasculitis. To establish the reason of the hereditary and acquired form of angioedema analyses of functional activity of complement components, quantities and activity of C1 inhibitor, presence (or absence) autoantibodies to C1 inhibitor allow. Sorption of the puried enzymes of activated subcomponent C1s or plasmin on micropanels allows to connect specifically in cells of plate C1 inhibitor from serum and with the help conjugate of antibodies against C1 inhibitor with a horse-radish peroxidase to determine quantity of connected functionally active C1 inhibitor. Addition of this test-system ELISA system for determination of quantitative contents of C1 inhibitor in serum, and also systems for definition IgG, IgA and IgM autoantibodies against C1 inhibitor finishes creation of a necessary set of methods of differential diagnostics.

Biological effects of C1 inhibitor

C1 inhibitor is a serine proteinase inhibitor (serpin) that regulates activation of both the complement and contact systems. Regulation of complement system activation takes place through inactivation of the classical pathway proteases, C1r and C1s, the lectin pathway protease, MASP2, and perhaps via inhibition of alternative pathway activation by reversible binding to C3b. Regulation of contact system activation takes place through inactivation of plasma kallikrein and coagulation factor XIIa. Deficiency of C1 inhibitor results in hereditary angioedema, which is characterized by recurrent episodes of localized angioedema of the skin, gastrointestinal mucosa or upper respiratory mucosa. A variety of clinical, in vitro and animal experiments indicate that the mediator of increased vascular permeability in hereditary angioedema is bradykinin. Animal models suggest that in addition to its utility in therapy of hereditary angioedema, C1 inhibitor may prove useful in a variety of other diseases including septic shock, reperfusion injury, hyperacute transplant rejection, traumatic and hemorrhagic shock, and the increased vascular permeability associated with thermal injury, interleukin-2 therapy and cardiopulmonary bypass. The therapeutic effect in these disease models very likely results from a combination of complement system activation, contact system activation and perhaps from other activities of C1 inhibitor. These other activities include a direct interaction with endotoxin, which may help to prevent endotoxic shock and an interaction with selectin molecules on endothelial cells, which may serve both to concentrate C1 inhibitor at sites of inflammation and to inhibit the transmigration of leukocytes across the endothelium.

Management of oral surgery in patients with hereditary or acquired angioedemas: review and case report

Angioedemas are a rare but significant event in simple oral surgery because they can cause an acute life-threatening laryngeal edema. We report a case of a tooth extraction in a patient with hereditary angioedema, for which the C1-inhibitor (C1-INH) concentration administered effectively controlled edema during and after extraction. We also review case reports of oral surgery management in patients with hereditary and acquired angioedemas. In 2 of 36 cases, laryngeal edema occurred after teeth extraction. One was considered to be a type 2 acquired angioedema, which tolerates replacement therapy with fresh frozen plasma. The other case was managed only with danazol, and it was suggested that this was on occasion insufficient. Safety of oral surgery on patients with angioedema depends on the type of angioedema and the availability of C1-INH concentration. An exact diagnosis of the type of angioedema is needed to know the effect of replacement therapy with C1-INH.

Hyperacute rejection of mouse lung by human blood: characterization of the model and the role of complement

BACKGROUND

The pathophysiology of hyperacute lung rejection (HALR) is not fully understood. A mouse model of HALR by human blood would be valuable to efficiently dissect the molecular mechanisms underlying this complex process, but it has not been described.

METHODS

We developed a xenogenic mouse lung-perfusion model. Perfusion with heparinized autologous blood (n=3) was compared with human blood unmodified (n=7) or pretreated with C1 inhibitor (n=5) or soluble complement receptor type 1 (n=6) at unchanged flow conditions.

RESULTS

Perfusion with autologous blood was associated with stable physiologic parameters and no overt evidence of lung injury for up to 2 hr. Pulmonary artery perfusion pressure increased rapidly after introduction of unmodified human blood, plasma anti-Gal(alpha)1,3Gal antibodies declined (90% immunoglobulin [Ig]M, 80% IgG), and lungs reliably met survival endpoints within 11 min (median 10 min, confidence interval [CI]: 9-11). Human Ig and neutrophils were rapidly sequestered in the lung. Survival was significantly prolonged in the soluble complement receptor type 1 group (36 min, CI: 26-46) (P<0.01) and in the C1 inhibitor group (23 min, CI: 21-25) (P<0.05), and pulmonary vascular resistance elevation and complement activation were significantly attenuated but not prevented.

CONCLUSIONS

Hyperacute rejection of mouse lung by human blood occurs with kinetics, physiology, and histology closely analogous to the pig-to-human model. In addition, as in that model, neither of two potent soluble-phase complement inhibitors prevented complement activation or HALR. We conclude that the mouse lung model is relevant to dissect the cellular and molecular mechanisms governing HALR.

The functional integrity of the serpin domain of C1-inhibitor depends on the unique N-terminal domain, as revealed by a pathological mutant

C1-inhibitor (C1-Inh) is a serine protease inhibitor (serpin) with a unique, non-conserved N-terminal domain of unknown function. Genetic deficiency of C1-Inh causes hereditary angioedema. A novel type of mutation (Delta 3) in exon 3 of the C1-Inh gene, resulting in deletion of Asp62-Thr116 in this unique domain, was encountered in a hereditary angioedema pedigree. Because the domain is supposedly not essential for inhibitory activity, the unexpected loss-of-function of this deletion mutant was further investigated. The Delta 3 mutant and three additional mutants starting at Pro76, Gly98, and Ser115, lacking increasing parts of the N-terminal domain, were produced recombinantly. C1-Inh76 and C1-Inh98 retained normal conformation and interaction kinetics with target proteases. In contrast, C1-Inh115 and Delta 3, which both lack the connection between the serpin and the non-serpin domain via two disulfide bridges, were completely non-functional because of a complex-like and multimeric conformation, as demonstrated by several criteria. The Delta 3 mutant also circulated in multimeric form in plasma from affected family members. The C1-Inh mutant reported here is unique in that deletion of an entire amino acid stretch from a domain not shared by other serpins leads to a loss-of-function. The deletion in the unique N-terminal domain results in a "multimerization phenotype" of C1-Inh, because of diminished stability of the central beta-sheet. This phenotype, as well as the location of the disulfide bridges between the serpin and the non-serpin domain of C1-Inh, suggests that the function of the N-terminal region may be similar to one of the effects of heparin in antithrombin III, maintenance of the metastable serpin conformation.

Laryngeal edema and death from asphyxiation after tooth extraction in four patients with hereditary angioedema

BACKGROUND

Recurrent angioedema is the hallmark of various inherited or acquired angioedema diseases. Hereditary angioedema, or HAE, due to C1 inhibitor, or C1NH, deficiency has considerable implications for dental health care providers because dental surgery may trigger distressing and even life-threatening episodes.

CASE DESCRIPTION

The authors reviewed the literature, focusing on the pathogenesis, clinical signs and treatment of HAE. They also provided case reports of four patients who died from laryngeal edema induced by tooth extraction. In patients with HAE, dental surgery--including tooth extraction--may be followed by self-limiting edema episodes, including lip swelling, facial swelling, tongue edema and laryngeal edema with upper airway obstruction. Preoperative prophylaxis has been performed with attenuated androgens, fresh frozen plasma, C1NH concentrate and antifibrinolytics. The four patients described underwent tooth extraction, which, after a symptom-free latency of four to 30 hours, provoked laryngeal edema. Three of the patients died of asphyxiation the night after surgery, and the fourth died on the second night. In three of the patients, laryngeal edema had not occurred previously.

CLINICAL IMPLICATIONS

Before undergoing dental surgery, patients with a history of recurrent angioedema should be evaluated for C1NH deficiency. If it is present, they are at risk of developing life-threatening laryngeal edema.

Administration of C1 inhibitor reduces neutrophil activation in patients with sepsis

Forty patients with severe sepsis or septic shock recently received C1 inhibitor. In the present study we studied the effect of C1 inhibitor therapy on circulating elastase-alpha(1)-antitrypsin complex (EA) and lactoferrin (LF) levels in these patients to gain further insight about agonists involved in the activation of neutrophils in human sepsis. Elevated levels of EA and LF were found in 65 and 85% of the septic patients, respectively. Patients with elevated EA levels had higher organ dysfunction scores, higher levels of cytokines, and higher levels of complement activation products than patients with normal EA levels. C1 inhibitor therapy reduced EA as well as complement activation and IL-8 release in the patients with elevated EA on admission. We conclude that neutrophil activation in human sepsis correlates with the severity of organ dysfunction and involves complement and interleukin-8 as agonists. The effect of C1 inhibitor therapy on neutrophils may provide an explanation for the beneficial, although mild, effects of this treatment on organ dysfunction in sepsis.

Autoantibodies and lymphoproliferative diseases in acquired C1-inhibitor deficiencies

Angioedema due to acquired C1-inhibitor (C1-INH) deficiency (also referred to as "acquired angioedema") is a rare, life-threatening disease with poorly defined etiology, therapy, and prognosis. To define the profile of acquired C1-INH deficiency and to facilitate the clinical approach to these patients, we report on 23 patients with acquired C1-INH deficiency followed for up to 24 years (median, 8 yr), and review the literature. We measured C1-INH activity with chromogenic assay and detected autoantibodies to C1-INH by enzyme-linked immunosorbent assay (ELISA). Median age at onset of angioedema was 57 years (range, 39-75 yr). All patients had C1-INH function and C4 antigen below 50% of normal. C1q was reduced in 17 patients. Autoantibodies to C1-INH were present in 17 patients. Long-term prophylaxis of attacks with danazol was effective in 2 of 6 patients, and with tranexamic acid, in 12 of 13 patients. Therapy with C1-INH plasma concentrate was necessary in 12 patients: 9 had rapid positive response and 3 became progressively resistant. Associated diseases at the last follow-up were non-Hodgkin lymphomas (3 patients), chronic lymphocytic leukemia (1 patient), breast cancer (1 patient), monoclonal gammopathies of uncertain significance (13 patients). In 4 patients no pathologic condition could be demonstrated. Compared with the general population, patients with acquired C1-INH deficiency present higher risk for B-cell malignancies, but not for progression of monoclonal gammopathies of uncertain significance to malignancy. Antifibrinolytic agents are more effective than attenuated androgens in long-term prophylaxis. Patients with acquired C1-INH deficiency may be resistant to replacement therapy with C1-INH plasma concentrate.

Angioedema and oral contraception

BACKGROUND

Oral contraceptives can precipitate attacks of hereditary angioedema (ANE) or induce acquired forms.

OBJECTIVE

We studied 5 patients who had an ANE which had begun under oral contraception and disappeared after stopping the pill.

METHODS

We explored the clinical and biological characteristics of these patients.

RESULTS

The symptoms developed during the first year or later after starting contraception; the patients reported relapsing swelling of the lips, hands, larynx and abdomen. All women had normal serum C4 and C1 inhibitor (C1Inh) antigen levels, but a lowered C1Inh activity, with a marked protein cleavage on the immunoblot. The suppression of the pill was associated with the regression of the edema and normalization of C1Inh function.

CONCLUSION

The mechanism of these ANE is unknown. The could be due to a modulation of C1Inh expression upon androgens or an imbalance between coagulation proteins favoring C1Inh cleavage by its target proteases.

Research on complement: old issues revisited and a novel sphere of influence

Immunology in recent years has taken a somewhat surprising turn, expressed by a renewed interest in innate immunity. Especially intriguing is the regulatory role exerted by the innate components on the adaptive response, with Toll receptors and complement components being the most investigated. This function has been firmly established for complement protein CR2 (CD21) as part of the BCR co-receptor CD19/CD21/CD81. New findings are now providing a broader picture of complement and its tuning of the immune response; for example, complement proteins have been implicated in the control of T-cell-mediated responses. We will review some of these data here and summarize new discoveries in areas of research on more traditional topics within the complement literature, such as complement and renal diseases, and the therapeutic use of C1-Inhibitor. We cover papers selected from studies presented at the XIX International Complement Workshop, held in Palermo in September 2002, and published within the past six months.

Recombinant human C1-inhibitor produced in Pichia pastoris has the same inhibitory capacity as plasma C1-inhibitor

Therapeutic application of the serpin C1-inhibitor (C1-Inh) in inflammatory diseases like sepsis, acute myocardial infarction and vascular leakage syndrome seems promising, but large doses may be required. Therefore, a high-yield recombinant expression system for C1-Inh is very interesting. Earlier attempts to produce high levels of C1-Inh resulted in predominantly inactive C1-Inh. We describe the high yield expression of rhC1-Inh in Pichia pastoris, with 180 mg/l active C1-Inh at maximum. On average, 30 mg/l of 80-100% active C1-Inh was obtained. Progress curves were used to study the interaction with C1s, kallikrein, coagulation factor XIIa and XIa, and demonstrated that rhC1-Inh had the same inhibitory capacity as plasma C1-Inh. Structural integrity, as monitored via heat stability, was comparable despite differences in extent and nature of glycosylation. We conclude that the P. pastoris system is capable of high-level production of functionally and structurally intact human C1 inhibitor.

Misdiagnosis of hereditary angio-oedema type 1 and type 2

BACKGROUND

Hereditary angio-oedema is a rare, life-threatening, autosomal dominant condition caused by deficiency (type 1) or dysfunction (type 2) of complement C1 inhibitor. Serological assays to measure C1 inhibitor concentration and function are widely available. However, expert interpretation may not be.

OBJECTIVE

To review all cases within three NHS Trusts with a putative diagnosis of hereditary angio-oedema.

METHOD

Review of laboratory results and clinical notes of 44 cases of presumed hereditary angio-oedema.

RESULTS

Audit revealed that 11 of 42 (26%) cases had been incorrectly considered to have a diagnosis of hereditary angio-oedema. Two of 44 had insufficient data to assess. All 11 had low functional C1 inhibitor recorded at presentation.

RESULTS

available in these 11 cases at the time of diagnosis showed a normal or borderline C4 level (>or= 50% of mean normal, in contrast to hereditary angio-oedema, where C4 was less than 40% of mean normal) indicating that the low C1 inhibitor levels were a result of sample decay. Cases incorrectly diagnosed were predominantly female and had a mean age at presentation of 40 years (compared with 22 years for type 1 hereditary angio-oedema). Six of the 11 cases were offered C1 inhibitor concentrate (pooled plasma product) as treatment.

CONCLUSION

We recommend that all suspected cases of hereditary angio-oedema are reviewed, that specialist advice is sought before making the diagnosis and that the diagnosis is only made after initial abnormal serology is confirmed on a second sample.

Complement components and their autoantibodies

The purpose of the immune system is to defend the host from constantly changing microbial pathogens. Autoimmune diseases develop as a consequence of the production of antibodies and/or cells that react with self-antigens, and may recruit other effector mechanisms that result in tissue damage. Thus, in this context, autoimmunity represents an immune response to self-antigens that is sufficient to cause disease. This article is specifically devoted to autoantibodies directed against complement components.

Prevention of cardiac cell injury during acute myocardial infarction: possible role for complement inhibition

The purpose of this article is to describe mechanisms of cell death in patients with acute myocardial infarction, particularly the activation of the complement system. Various pro-inflammatory cytokines, released by the inflamed tissue, play a role in the activation of the complement system. Several complement inhibitors have been developed to reduce tissue damage following ischemia. According to animal studies the deleterious effects of activators of the complement system can be diminished by complement inhibition. Several clinical studies have been conducted for the potential treatment of cell injury during acute myocardial infarction. C1 inhibitor dose-dependently inhibited complement activation and appeared to reduce myocardial injury after reperfusion therapy in patients with acute myocardial infarction. C1 inhibitor dose-dependently reduced plasma levels of C4 activation fragments. In addition, cardiac enzymes (troponin T and creatine kinase-MB) returned to baseline levels more rapidly among patients treated with C1 inhibitor, compared with controls. Furthermore, preliminary results from a placebo-controlled trial indicate that treatment with intravenous pexelizumab (anti-C5 antibody) was well tolerated in a large number of patients undergoing coronary artery bypass graft surgery. Further, more randomized trials are necessary to clarify the clinical significance of this new and innovative treatment with complement inhibition.

Nuclear phosphatases and the proteasome in suppression of STAT1 activity in hepatocytes

IFN-gamma induction of C1 inhibitor (C1INH) is mediated by an IFN-gamma-activated sequence (GAS), via binding of signal transducer and activator of transcription 1 (STAT1). These studies focused on the factors responsible for down-regulation of nuclear STAT1 in hepatocytes, the primary site of synthesis of C1INH. The activity of nuclear STAT1 following stimulation with IFN-gamma was sustained with the phosphatase inhibitor, pervanadate, or the proteasome inhibitor, lactacystin. Pervanadate prolonged STAT1 activation and blocked the inactivation of nuclear STAT1. Binding of ubiquitin to phosphorylated STAT1 was detectable in cells treated with lactacystin. Staurosporine only moderately decreased the prolongation of nuclear phosphorylated STAT1 after pretreatment with pervanadate or lactacystin. An antisense mitogen-activated protein kinase phosphatase (MKP-1) oligonucleotide prolonged the accumulation of phosphorylated STAT1. These data are consistent with the hypothesis that down-regulation of IFN-gamma-mediated nuclear STAT1 binding in hepatocytes involves both dephosphorylation by MKP-1 and degradation via proteolysis by the ubiquitin-dependent proteasome pathway.

Increased susceptibility of the left compared to the right ventricle to remote ischemia/reperfusion injury in human C1-inhibitor-overexpressing transgene mice

Acute myocardial injury has been demonstrated as a remote sequela of severe lower torso ischemia-reperfusion (I/R) due to proinflammatory events. In a model of I/R injury, administration of C1 esterase inhibitor (C1-Inh) reduces myocardial necrosis. We investigated the susceptibility of the left (LV) versus right ventricle (RV) and the protective effect of transgenic C1-Inh-overexpressing mice. Two groups of mice (n = 6) underwent a 2-h lower torso ischemia followed by 3 h of reperfusion: transgenic and wild type with sham-operated controls. Animals were then injected with (125)I bovine albumin. Heart was removed and samples from right and left ventricular free wall were harvested, weighted, and radioactivity was determined. Permeability index for wild-type animals in the RV was 0.22 +/- 0.04, compared to 0.17 +/- 0.07 in controls (NS), and in the LV 0.36 +/- 0.08, compared to 0.21 +/- 0.05 in controls (p <.01). The LV showed a significantly higher value compared to the right (0.22 +/- 0.04 vs. 0.36 +/- 0.08, p <.01). No difference was seen in the RV between transgenic and wild-type mice; however, in the LV the values decreased significantly in transgenic animals (p <.015). Thus, remote myocardial injury after lower torso I/R is present in both ventricles; however, the LV seems to be more susceptible as assessed by albumin permeability. Inhibition of the classic complement cascade may be a promising therapeutic approach for myocardial protection in reperfusion injury.

Normal transcription of the C1 inhibitor gene is dependent upon a polypurine-polypyrimidine region within the promoter

Analysis of the transcriptional activity of C1 inhibitor (CIINH) promoter reporter constructs with mutations in the R-Y region indicate that triplex formation by this region is not a predictor of transcriptional activity and that normal promoter function depends on the interaction of trans acting factors with specific elements within this region. Electrophoretic mobility shift assay (EMSA) of Hep3B nuclear extracts using the wild type promoter probe (nucleotides -98 to -9) yielded four major bands. Incubation of the same extracts with probes lacking the HNF-1 site resulted in the disappearance of one band. Supershift assays indicate that HNF-1alpha is the only previously identified protein that is present in the EMSA bands. Southwestern blot analysis detected four bands (M(r)s -130, 75, 65 and 20 kDa). These data suggest that the -98 to -9 region of the C1INH promoter interacts with at least four proteins, one of which is HNF-1alpha.

Complement component C5: engineering of a mutant that is specifically cleaved by the C4-specific C1s protease

Previous studies showed that simply inserting or substituting a few amino acid residues immediately downstream of the proteolytic activation site in C component C3 renders that site susceptible to the C4-specific C1s protease. This report describes the results of extending those studies to the closely related component C5. We found that small changes, similar to those that made C3 susceptible to C1s, were insufficient to render C5 C1s-sensitive; and neither more extensive substitution downstream of the cleavage site with a 14 residue long segment from C4, nor upstream substitution with an 8 residue long C4 segment gave C1s cleavage. However, substitution of both the upstream and downstream segments gave a hybrid C5 protein, designated ASC4, which was cleaved by C1s. The protease sensitivity of ASC4 was curious, however, in that C1s was more active against the secreted extracellular biosynthetic precursor, pro-ASC4(E) than mature ASC4, whereas a C5-specific convertase cleaved the mature protein but not the precursor. In contrast, both mature and precursor forms of wild-type C5 were cleaved by the C5 convertase, but neither of course is recognized by C1s. These results demonstrate that a mutant C5 molecule can be constructed that is cleaved at the activation site by both C1s and C5 convertase. This suggests that the structures necessary for specific recognition by the two proteases have little or no overlap and that recognition by C5 convertase involves residues that are distant from the activation site itself.

Kinetic differentiation between enzyme inactivation involving complex-formation with the inactivator and that involving a conformation-change step

It has been suggested that the complexing type of inactivation in which the inactivator binds reversibly with the enzyme before inactivation cannot be differentiated kinetically from that a slow enzyme conformation change is involved as a first step [Rakitzis (1986) J. Theor. Biol. 122, 247-249]. The kinetics of the substrate reaction during modification of enzyme activity previously described [Tsou (1988) Adv. Enzymol. Relat. Areas Mol. Biol. 61, 381-436] have now been applied to this problem and equations derived to show that the slow-conformational-change type can be differentiated from the complexing type by plotting the final concentration of product formed, [P]infinity, against the reciprocal of inactivator concentration. The reaction of hexokinase with 2-chloromercuri-4-nitrophenol has been shown to involve a conformational change of the enzyme before inactivation.

Erythromycin inhibits Cl secretion across canine tracheal epithelial cells

We studied the effect of the macrolide antibiotic erythromycin on bioelectrical properties of canine cultured tracheal epithelium under short-circuit conditions in vitro. Addition of erythromycin to the submucosal but not to the mucosal side dose-dependently decreased short-circuit current (Isc), the maximal decrease from the baseline value and the concentration required to produce a half-maximal effect (IC50) being 5.6 +/- 1.0 microA.cm-2 (mean +/- SE, p less than 0.001) and 18 microM, respectively. In contrast, other antibiotics including ampicillin, cephazolin and tetracycline were without effect. The erythromycin-induced decrease in Isc was not altered by amiloride, but it was abolished by bumetanide, diphenylamine-2-carboxylate2, and substitution of Cl in the bathing medium with gluconate (p less than 0.001, in each case). The effect of erythromycin on epithelial Isc was attenuated by pretreatment of cells with indomethacin but not with AA-861 a lipoxygenase inhibitor. Incubation of cells with erythromycin inhibited the release of prostaglandins E2 and F2 alpha from tracheal epithelial cells. These results indicate that erythromycin may selectively inhibit Cl secretion across airway epithelium through the inhibition of prostaglandin synthesis and suggest that this action possibly reflects its clinical efficacy in the treatment of airway hypersecretion.